The instant invention relates to a lifting tong toggle lock adapted to be cooperatively employed in combination with a simple tong grab toggle structure that is provided with a tong latch for alternately holding the load engaging tong grapple members of the lifting tong structure in either an open position for purposes of accepting a load or releasing the lifting tong such that the pivotally assembled toggle arms thereof may thereupon symmetrically extend to pivotally close the tong arms for grappling engagement upon a load, wherein the teaching set forth by Heppenstall in U.S. Pat. No. 1,839,389 dated Jan. 5, 1932, is generally that type of a tong grab toggle structure with tong latch assembly upon which the instant invention may be employed in combination, although it is to be further understood that the instant invention may also be employed in combination with other types of simple tong grab toggle structures having a tong latch exemplary of which would be those as variously illustrated and taught in U.S. Pat. No. 1,506,827 to Gellert dated Sept. 2, 1924, with the understanding that by specific reference to the foregoing teachings the same are intended not to thereby be structurally restrictive of those specific types of simple tong grab toggles with tong latches with which the instant invention may be employed in combination, but exemplary only as are also to be regarded the representative renditions of such structures as herein illustrated.
Functionally, a simple tong grab structure as herein identified is operated to release a load engaged thereby by the operator thereof permitting the load to come to rest upon a support surface such as to cause a slackening of the tong suspending cable, as from an overhead crane or the like, both the tong like arms and tong arms of said grab structures symmetrically move downwardly thus pivotally opening the scissor-acting tong arm from engagement with the load and thereby releasing the load. In certain circumstances, however, as when attempting to jockey a tong suspended load into a confined position for storage stacking or the like, or when it is necessary to locate and position a vertically elongated tong suspended load, such as an ingot or the like, in a horizontally stacked configuration for storage or subsequent processing operations, one does not want the tong structure to collapse and thereby release the load upon an intermediate resting thereof upon a support surface prior to final positioning manipulation for load release, in which event either a floor tender is required to facilitate rehooking of the tong arm grabs to a load should the crane operator accidentally or inadvertently permit the tong structure to collapse during an intermediate support surface load resting stop, or some sort of mechanical lock assembly is necessary to maintain the loaded tong in an erected load carrying configuration irrespective of whether the load itself may be intermediately rested upon a support surface and until such time as the lock assembly is deliberately released whereby the tong structure is thereby enabled to collapse and disengage the load.
For purposes of labor economy and safety, employment of a mechanical tong lock assembly for maintaining the load is preferred to use of floor tender personnel, in which regard the following such devices, heretofore known, whereby tong grapple members may be locked in a particular position relative to the load to be carried, or carried thereby, said devices being as respectively taught in French Pat. No. 790,821 to Bertheaud dated Nov. 28, 1935, U.K. Pat. No. 709,438 to Davidson dated May 26, 1954, and U.S. Pat. No. 2,803,489 to Zito et al dated Aug. 20, 1957.
With respect to a rack and pinion structure having a ratchet wheel with cooperative locking and release pawl in combination therewith, Danish Pat. No. 25,407 to Riddersborg dated Dec. 22, 1919, teaches such a structure in a device employed to force open, and hold open, the abdominal body cavity of a slaughtered animal.
In French Pat. No. 1,230,272 to Boyer, dated Sept. 14, 1960, a rack and pinion crane clamp structure, activated to close and compressively engage and retain a load carried thereby upon elevation of the crane, is shown and taught.
Functionally, ratchet shaft grapple clamp locking and release means are as respectively shown and taught in U.S. Pat. No. 1,472,081 to Mercer dated Oct. 30, 1923, and U.S. Pat. No. 1,492,999 dated May 6, 1924, also to Mercer.
Some of the features of the instant invention have, in some respects, both structural and/or functional similarities to various of those teachings separately set forth in the prior art disclosures heretofore cited and briefly discussed. However, as will hereinafter be pointed out, the instant invention is distinguishable from said earlier inventions in one or more ways in that the present invention has utility features and new and useful advantages, applications, and improvements in the art of lifting tong toggle locking means not heretofore shown.